Antarctic Bottom Water (AABW), which supplies the lower limb of the thermohaline circulation, originates from dense shelf water (DSW) forming in Antarctic polynyas. Here, combining a long mooring record of DSW measurements with numerical simulations and satellite data, we show that significant correlation exists between interannual variability of DSW production in the Ross Sea polynyas, where DSW contributes between 20–40% of the global AABW production, and the Southern Annular Mode (SAM). The correlation is largest when the Amundsen Sea Low (ASL) is weakened and shifted east of the Ross Sea. During positive SAM phases, enhanced offshore winds and lower air temperatures over the western Ross Sea increase sea ice production and promote DSW formation, with the opposite response during negative SAM phases. These processes ultimately modulate AABW thickness in the open ocean. A projected positive shift of the SAM and eastward displacement of the ASL thus has implications for the future of DSW and AABW formation.

Ice shelves in the Amundsen Sea have experienced the most rapid melting in the Antarctic and are expected to accelerate throughout this century under climate warming. In this study, a high‐resolution ocean‐sea ice‐ice shelf model is employed to conduct sensitivity experiments to explore the effects of increasing melt rates of the Amundsen Sea ice shelves on hydrography, sea ice and ice shelf in the Ross Sea. The results indicate that the substantial inflow of meltwater significantly freshens the Ross Sea, inhibiting the formation and export of the Dense Shelf Water, the volume of which is reduced by 19%–33% on the shelf. Temperatures in the eastern and western Ross Sea exhibit different responses to the enhanced meltwater input. The freshening of the western Ross Sea weakens the mesoscale eddy activities which are efficient in carrying warm Circumpolar Deep Water onto the shelf, leading to an average temperature decrease of 0.02–0.08°C. Conversely, in the eastern Ross Sea, there is a marked warming outside the shelf under increased meltwater, which results from zonal pressure gradients associated with the meltwater distributions. This consequently causes stronger on‐shelf heat transport and shows warming of 0.12–0.22°C on the eastern Ross Sea shelf. The narrow shelf in the eastern Ross Sea allows the warmer water to reach the Ross Ice Shelf (RIS) front, resulting in an about 6%–9% increase in the RIS melting. These results suggest a possible mechanism for acceleration in the RIS melting in the future that is associated with enhanced meltwater inflow.

The Ross Sea in the Southern Ocean is a key region for the Antarctic Bottom Water (AABW) production, primarily originating from the Dense Shelf Water (DSW) formed in polynyas. Here we project future changes in DSW and AABW production in the Ross Sea using a high‐resolution ocean‐sea ice‐ice shelf coupled model that can well capture the observed DSW temporal variability, forced by projected atmospheric perturbations from the CMIP6 multi‐model mean results. Under the high‐emissions scenario, the volume of DSW in the Ross Sea will decrease by ∼26% by 2051–2060 and by ∼51% by 2091–2100 relative to the present, resulting in a reduction of AABW thicknesses by up to 300 m. Such reduction is a combined result of decreased local sea ice production and increased meltwater from the Amundsen Sea ice shelves, which freshens the upper layer of the western Ross Sea and inhibits deep ocean convection.

The Ross Sea in the Southern Ocean is a key region for the formation of the Antarctic Bottom Water (AABW) that supplies the lower limb of the global overturning circulation and contributes to 20 %–40 % of the total AABW production. AABW primarily originates from polynyas characterized by strong sea ice production and ocean convection that lead to the formation of Dense Shelf Water (DSW), the precursor of AABW. The production and characteristics of DSW in the Ross Sea and AABW in the surrounding ocean are significantly affected by ice shelf meltwater transported from the nearby Amundsen Sea. The scarcity of long-term observations in the Ross Sea hinders the understanding of DSW and AABW variability, and numerical models are needed to explore the multi-scale variations in these water masses and the forcing mechanisms. In this work, a coupled high-resolution ocean–sea ice–ice shelf model is developed for the Ross Sea and Amundsen Sea, named the Ross Sea and Amundsen Sea Ice–Sea Model (RAISE). Detailed descriptions of the model configurations are provided. This study represents an attempt to thoroughly evaluate the DSW properties and associated ocean–sea ice–ice shelf coupling processes among modeling studies in the Southern Ocean, using multiple datasets including satellite-based observations and hydrographic measurements from the World Ocean Database, Argo profilers and seal-tag sensors. In particular, the modeled temporal variations in DSW properties in polynyas and key export passages are compared with long-term mooring observations, which are rarely seen in studies of the DSW temporal variability before. RAISE demonstrates a high skill level in simulating the observed sea ice production rates in the Ross Sea polynyas, and the modeled spatial and temporal variability in DSW are significantly and strongly correlated with observations. RAISE can also effectively capture the observed long-term freshening trend of DSW prior to 2014 and the rebounding of DSW salinity after 2014. RAISE shows an overestimate of DSW density in the Ross Sea, which is associated with an underestimate of ice shelf melting rates in the Amundsen Sea, missing ice shelf calving processes and subglacial discharge in the model. A sensitivity experiment simulating increased freshwater discharge from these processes can significantly improve the simulation of DSW properties.

The East China Shelf Seas, comprising the Bohai Sea, the Yellow Sea, and the shelf region of East China Sea, play significant roles among the shelf seas of the Western North Pacific Ocean. The projection of sea surface temperature (SST) changes in these regions is a hot research topic in marine science. However, this is a very difficult task due to the lack of available long-term projection data. Recently, with the high development of simulation technology based on numerical models, the model intercomparison projects, e.g., Phase 5 of the Climate Model Intercomparison Project (CMIP5), have become important ways of understanding climate changes. CMIP5 provides multiple models that can be used to estimate SST changes by 2100 under different representative concentration pathways (RCPs). This paper developed a CMIP5-based SST investigation framework for the projection of decadal and seasonal variation of SST in East China Shelf Seas by 2100. Since the simulation results of CMIP5 models may have degrees of errors, this paper uses hydrological observation data from World Ocean Atlas 2018 (WOA18) for model validation and correction. This paper selects seven representative ones including ACCESS1.3, CCSM4, FIO-ESM, CESM1-CAM5, CMCC-CMS, NorESM1-ME, and Max Planck Institute Earth System Model of medium resolution (MPI-ESM-MR). The decadal and seasonal SST changes in the next 100 years (2030, 2060, 2090) are investigated by comparing with the present analysis in 2010. The experimental results demonstrate that SST will increase significantly by 2100: the decadal SST will increase by about 1.55 °C, while the seasonal SST will increase by 1.03–1.95 °C.

The northern Antarctic Peninsula (NAP) region is a highly productive ecosystem that supports a large krill‐based food web. In summer 2006, the NAP region had substantially elevated phytoplankton biomass, with surface chlorophyll‐a concentrations that reached the greatest level during 2001–2023. Using the long‐term in situ data from the U.S. Antarctic Marine Living Resources program, satellite observations, and ERA5 reanalysis products, the mechanisms of the elevated chlorophyll‐a anomalies in summer 2006 were analyzed. The results suggest that the position of the Amundsen Sea Low (ASL) shifted considerably westward that summer, resulting in strong positive sea level pressure anomalies west of the NAP, which induced southerly wind anomalies and reduced the advection of moist airflow toward the NAP. This in turn reduced the cloud coverage and increased photosynthetically available radiation over this region, which directly increased the phytoplankton photosynthesis. The intensified radiation also increased the ocean temperature and strengthened stratification, which increased phytoplankton growth rates and allowed phytoplankton to accumulate in the upper euphotic zone. This work underlines the important role of coupled atmospheric‐oceanic processes in generating large phytoplankton biomass in the NAP region.